The present invention pertains to a flue box assembly for use in conjunction with heating plants which is designed to insure the complete combustion of the fuels in a heating plant for energy conservation purposes, and improved heat transfer to optimize energy conservation.
Heretofore, flue box assemblies have been developed for installation along the outlet exhaust pipes emanating from a heating plant, the flue box being designed to insure the complete combustion of the fuels utilized in connection with a heating plant. It has been known, for example, that in a typical heating plant, a certain percentage of the fuels provided to the heating plant will remain unburned and will escape from the heating plant along with the flue gases representing the products of combustion of that portion of the fuel which has in fact been combusted. In addition, the heat transfer process is substantially reduced, thereby creating an improper balance in the combustion zone. In general, flue boxes of this nature have heretofore been developed as shown by U.S. Pat. No. 4,372,289 as well as U.S. Pat. No. 4,136,676. As is clearly described therein, the flue box is designed with a pivotally movable damper plate located within the interior portion of the housing of the flue box assembly, the damper plate being movable between an open and closed position. Under normal conditions, the damper plate will stay substantially closed, and will block the flow path of the flue gases being exhausted from the heating plant. Since these flue gases contain unburned fuels as well, the gases are restrained in the heating plant such that a more complete combustion of the fuels will be achieved, and better heat transfer attained. Furthermore, by having the damper plate pivotally movable therein, under conditions of extreme back pressure or explosion, the damper plate is designed to pivotally move to a complete open position thereby to provide an immediate exit path for the flue gases emanating from the heating plant.
Further improvements have been achieved by creating the flue box assembly having a greater diametric opening than either the inlet or outlet openings therefrom. Hence, it has been found that by providing an expanded chamber for the flue gases to enter the flue box from the heating plant, stratification of the denser unburned fuel products near the surfaces of the flue box and the exhaust conduit will occur. As hot exhaust gases are produced, a channeling effect occurs wherein a central column of hotter gas is created which may cause a build-up of the unburned fuel vapors below the damper plate in the flue box assembly. Hence, further efficiencies in connection with energy conservation can be effected where the damper plate is provided with one or more flue openings or apertures positioned therein thereby avoiding or minimizing the danger of back pressure of the unburned gases or other gases caused by stratification under the damper plate.
It has further been observed that in some installations, it is necessary to provide the flue box with an additional device in order to insure that the unburned fuels will in fact be forced back into the furnace for total combustion. In this connection, it has now been found that by providing the flue box with a pivotal cap, which is designed to move between an open and a closed position thereby either occluding, or rendering the outlet opening from the flue box unobstructed, further efficiency of fuel combustion is achieved, including an increased efficiency in heat transfer and the restoration of proper combustion zone balance. This is especially true when the pivotal cap is provided on a flue box of the type having a pivotal damper plate mounted therein. However, in order to provide a cap for a flue box assembly, it is again necessary that the cap not only be pivotally adjustable, thereby to move between an unobstructed open position, and an occluded closed position relative to the flue box, but that the cap must be designed to achieve a delicate counterbalancing relationship with respect to the pressure of the flue gases exiting from the furnace via the flue box assembly.